How to Convert 5e Players: The World Within a World Strategy

I'm going to lead with this: if someone is happy with 5e, they're going to stay with 5e. But, maybe, possibly, you can get them to TRY another game, and maybe they can learn to appreciate another game! I have had an epiphany!

I can't be the only person who has ever had the idea "what if our D&D characters made their own D&D characters and played D&D? How meta!"

The premise: You give the players characters (not the players) a situation in your game where they can play another TTRPG for a reward. A reward is better than avoiding a consequence, but you can layer both. Maybe a traveling magical stranger come along and offers the PCs a chance to play a magical game for fabulous prizes. Maybe they meet a mad wizard who got trapped in a secondary world, that is to say, a world within a world like the Matrix or some Isekai. That secondary world has different rules. To go into that world, the characters will have to play by those rules - like the Savage Worlds, Shadowrun, Shadowdark, or GURPS or whatever. I'm sure you can make up a situation that suits your own game.

Tips:

Use incentives! If their 5e D&D characters can complete the 1e D&D adventure you have prepared for them, their 5e characters can magically keep a magic item their 1e characters earned. Offer them something NICE like a +3 item.

Make sure it's a choice! Don't force it on them. But you could.

Split the party. Its magical wibbly-wobbly timey-whimey BS and it doesn't interfere with normal passage of time. Don't let a pesky thing like democracy stop willing players. Run a side-game for them. Work around the party-poopers so they don't feel spurred.

Make the medicine sweeter! Don't just give them a loser 1e D&D character sheet, give them a really impressed 1e D&D character sheet. Unless they'd be into a character funnel.

Justification: Maybe the players need a palate cleanser; Do this instead of a one-shot. Maybe they've just finished an adventure and you don't have the next adventure prepped yet. This is your excuse for delaying.

Have respect for their time: Structure this like a one-shot! Try to keep it to a one-session thing.

Leave them wanting more: At the end of the PCs brief stint into the secondary world, when everything feels wrapped up, you're going to give them another adventure hook! Like a treasure map to a ruin with a ton of treasure, or their own star ship.

Make it Easy: Hand out pre-generated characters. Don't spend game time making characters. Leave out some of the more complex options.